Lakes, ponds and rivers are warming up more rapidly than the air. Many already surpassed the 1.5 degrees Celsius increase that nations agreed to try to avoid – in the air – under the 2015 Paris agreement. “Being in hot water” also means being in trouble and this is certainly the case. The combination of warming and the ongoing eutrophication (addition of nutrients, such as fertilizer from agriculture) of surface waters worldwide leads to bad water quality and a “less than good” ecological condition. Within Europe, this is particularly the case in the Netherlands.
Research of prof. Kosten and collaborators shows that in surface waters around the globe eutrophic and warm waters emit substantial amounts of greenhouse gases, particularly of the strong but short-lived greenhouse gas methane. This points at a self-enforcing feedback: warming and eutrophication enforce climate change, which in turn increases warming and eutrophication.
This gloomy finding contains an optimistic message: research has demonstrated that if we manage to combat eutrophication and especially when we can protect or re-establish submerged vegetation we can considerably reduce aquatic methane emissions. Kosten’s work also shows that not all vegetation is equally effective in achieving this effect: algae and duckweed thrive in eutrophic waters and do not improve the water quality, but submerged water plants can help combat the methane emissions from the sediment and the water.
View the lecture part at 16:58 minutes to get an idea of how methane is emitted from water. Text continues under the video.
